1. Field of the Invention
The invention relates to a method for broadcasting a stream of messages, including messages of a predetermined type.
The invention also relates to a system for transmitting and receiving a stream of messages.
The invention further relates to a transmitter for transmitting a stream of messages, including messages of a predetermined type.
Furthermore, the invention relates to a receiver for receiving a stream of messages, including messages of a predetermined type.
2. Description of the Related Art
Such a method and system are known from "Specification of the radio data system (RDS)", EN50067:1992, by CENELEC, Brussels. The Radio Data System is a system for broadcasting digital RDS data together with an analog signal. This RDS data may comprise several kinds of information, for example, data on the network transmitting the program signal, data on networks linked to the present network for, e.g., traffic information (Enhanced Other Networks), paging data, radio text, etc. In fact, the RDS allows various kinds of data services to be provided to a listener, especially through the newly defined Open Data application, which allows an RDS group type to carry any kind of data service allocated to that group type with a 3A group. Normally, a receiver receiving RDS data is continuously tuned to a particular network (using the AF feature provided by RDS) and is capable of practically continuous reception of RDS data. Sometimes the receiver has to switch over to another tuning frequency, for instance, when the Enhanced Other Network feature, indicated in groups of type 14, signals that traffic information is broadcast on another network. The switch-over may also be used for checking reception quality on other frequencies. During such a switch-over, the receiver cannot receive the RDS data provided at the original frequency to which the receiver was tuned. For example, when a listener is interested in RDS TMC messages, which are provided in group type 8A, the listener may miss some of these RDS TMC messages, which were broadcast at the original frequency during the time the receiver has switched over to another frequency.